1. Field of the Invention
The present invention relates to a solar cell module suitable for power generation, more specifically, to a solar cell module which has light weight but is still sufficiently mechanically strong for practical use.
2. Description of the Related Art
Solar cell modules (hereinafter also simply referred to as a "module"), are known in which structural members of tempered glass used as a transparent window and a metal sheet or the like used as a sealing member, are adhered to each other by polyvinyl butyral or ethylene vinyl acetate resin as a pottant and are sealed with a metal or plastic frame (for example, Takahashi and Konagai "Amorphous Solar Cells", published by Shokodo, pp 17-18).
Modules having the structure mentioned-above are necessarily heavy, and therefore, the foundation and mounting thereof must be mechanically very strong in order to support such heavy modules when installed as an array. Solar power generation costs include not only the cost of the module but also the cost for such additional structural members or portions. To bring the costs of solar power generation to a practical level, the cost of the additional structural members or portions and the cost of a module must be reduced.
In consideration of the above, it has been proposed to use, between the solar power generation element and the sealing member, an aluminum honeycomb structure, a paper honeycomb or a rib structure as a supporting member for supporting the sealing member and for withstanding wind pressure. The use of such a supporting member reduces both the weight of the module and the load on the foundation and the mounting of an array. Thus, a reduction of cost for the structural members or portions is attained. (see, K. Kurokawa et al "Development of Large-Size and Light-Weight PV Modules Reinforced by Paper Honeycomb Structure", Technical Digest of the International PV SEC-1, Kobe, Japan, pp (665-668)
Nevertheless, a tempered glass sheet having a thickness of not less than 3.2 mm must be used as the transparent window member to ensure sufficient strength against hailstorms and wind pressure. Particularly, if an amorphous solar cell made on a glass substrate is used, the glass substrate and the window on the side from which sunlight is incident constitute double glass sheets. This construction necessarily places a limit on the lightening of the module. Moreover, the honeycomb or rib structure mentioned above functions as a thermal insulation layer and causes an increase of the surface temperature of the solar cells, thereby reducing the photoelectric conversion efficiency.